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Old 04-24-2009, 11:40 AM   #1
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Questions?? can a servo be made into an ESC

hello,
i heard that a sevo could be transformed into an ESC, i wa just wondering wether anyone else had heard this and are in posession of the correct method as i cannot find it anywhere(all sites say sometyhing dufferent)
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Old 04-24-2009, 11:49 AM   #2
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well, you COULD mean a mechanical speed control, where the servo moves an arm over a circuit board with resistors connected to it.

But an ESC? no. well, maybe a really really really small one for cars with pager motors...
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Old 04-24-2009, 11:49 AM   #3
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Must be possible but i think that it useless.
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Old 04-24-2009, 11:56 AM   #4
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http://www.steeldecknavy.com/speed.jpg

here u go a mechanical speed control
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Old 04-24-2009, 12:28 PM   #5
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Maybe for a micro RC YES...

Because if you hook up a 4.8v or 6v battery to a reciever and hook up two servos they will both work (nitro setup) but if you get the throttle servo and take out the motor (just the motor) you could you use it with a "rwd" and "revurs" motion. But speeds would be slow and with a direct motor output wouldn't have much torque. (Unless you use the gears of the servo for torque and biuld a mini crawler )


So i think it is possible. A servo "could" be converted to an ESC 100%.
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Old 04-24-2009, 12:30 PM   #6
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All you can use from the servo is the signal decoding part. You then need a signal amplifier and then a final power stage to drive the motor. All this you would have to build yourself. If you're a good electronics engineer (diplom) you can do it. Silicon Chip run a story some years back about the guy who designed and built the R/C machines they used in shooting the first Starwars series, but back then all that was necessary because it didn't exist comercially. These days, you can buy stuff ten times more complex than that with a couple of hundred bucks and you wouldn't even be competitive.
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Old 04-24-2009, 02:02 PM   #7
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Quote:
Originally Posted by niznai View Post
All you can use from the servo is the signal decoding part. You then need a signal amplifier and then a final power stage to drive the motor. All this you would have to build yourself. If you're a good electronics engineer (diplom) you can do it. Silicon Chip run a story some years back about the guy who designed and built the R/C machines they used in shooting the first Starwars series, but back then all that was necessary because it didn't exist comercially. These days, you can buy stuff ten times more complex than that with a couple of hundred bucks and you wouldn't even be competitive.
Diploma to build ESC now I have none and have done that.
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Old 04-24-2009, 02:06 PM   #8
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I've actually turned a servo is a very primitive speed controller quite some time ago. I took out the motors and gears, and connected the motor leads to the trigger leads of a relay (I think it was a 9v relay from my 140-in-1 ket) with the battery/motor to the current side. It was then possible to adjust the trim so that it would be sitting still and you could hear the relay clicking open and shut very quickly, making it sound like there was something revving in the car. When I pulled the throttle, the relay would engage sending the power from the battery to the motor - the only problem being it was always full power, there was no throttle control whatsoever.. It was fun for a while to tear around with it in a buggy...
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Old 04-24-2009, 03:00 PM   #9
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Yes you can... a servo circuit board can be use as a low power esc... try google-ing it... the circuit board would become a forward-reverse esc but only for low amp application....

Check this out...

http://www.nyblimp.com/articles/ESC.htm
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Old 04-24-2009, 11:23 PM   #10
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Quote:
Originally Posted by Logika View Post
Diploma to build ESC now I have none and have done that.
Did you actually design your own or picked up the kit or wiring diagram and built it? I have put together kits and built things after diagrams but designing something that actually does what you want it to (as opposed to what IT wants to) is a different matter. Just like the difference between making (i.e. design, manufacture, assemble, test, fine tune and run) your car and putting together a car kit you bought from the shop.

A lot of people here seem to believe you can use the servo as a small current esc. That is true, but has very limited (if any) practicality (someone already pointed this out). My answer is hinting what you can really do to get a real esc out of a servo. Short of that you're just bodging something with no use.
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Old 04-25-2009, 10:22 PM   #11
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Default Servo to ESC

Boy this discussion brings back some memories!!! Since I'm so old and have been involved inmost phases of RC Car Racing since about 1970, I can tell you that it is not only possible but was angiant leap forward!

Some quick background: The first 1/12 scale R/C cars were nitro (we called them "gas") with Cox .049 engines and hard plastic bodies...Jerobee Cars. those of us in the the Midwest couldn't race 1/8 gas in the winter and some guys started converting the Jerobee cars to electric. All you needed was a Black & Decker 4.8volt hand-held grass trimmer to go with the Jerobee chassis. My recollection is that Fort Wanye, Indiana, (Wayne Palmer?) Chicago (Roy Moody) and Toledo and Detroit were into this pretty early. There were many early speed controls, I remember Roy's cars using a series of micro-switches and resistors actuated by a "camshaft" connected to a servo. 1/8" Wheel collars on a 1/16" shaft made the cam lobes and switched in 2 resistors, one resistor, and no resistor for 3 speeds! I remember some modified slot car controller resistor/wiper set-ups Rick Davis out of Detroit used and that style became the standard, even had adjustable dynamic brakes!!!
Now to the Servo/ESC. The first one I saw was in Fort Wayne and unfortunately I can't remember the guys name (Rick?) Great guy, neat cars, good driver, and very helpful. He had this very smooth control in his car and it worked really well. (Oh yeah, I think we were still running on slippery floors then with soft foam tires coated with silicone, smooth was good!!) Anyway he gave me the plans and I made some up and some of us in Toledo ran them. I have some of the parts left in my elecronics junk box. It used a Motorola S2000 Power transistor, driven by the servo amplifier removed from the servo. I think there were a few other parts but basically the transistor replaced the motor in the servo and regulated the voltage to the drive motor. We were using Mabuchi can motors, very similar to the closed end bell ones many manufacturers use in the RTR's.

Hey, that reminds me of one ya'll never believe!! We also used a rotary selector switch, kinda like an old click TV tuner, with resistors dropping the voltage to the motor. But before the resistors, we would wire it so first one cell, then two cells, then three cells, THEN all four were switched on for a FOUR Speed Controller!!! Can you even imagine what that did to the balance of the Batteries??? Just about everybody had the cells hard wired into the car and charged for 15minutes between heats. The early chargers were pieces of wire with alligator clips used to limit the current to the pack, then 15 minute timers were added for automatic cut-off. When digital Volt meters came out you could peak charge while watching the rate of voltage increase and then the voltage drop after peak. I swear this is all true!!!

Those were the good old days!!!

Happy Racing,
Ned
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Old 07-25-2011, 08:43 AM   #12
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Yes, it is in fact possible and *shock* you don't need a diploma to do it. Just a soldering iron.

Just 1)tear down the servo,
2)strip off the motor,
3) solder an h-bridge (l293d or perhaps a custom higher-current one) where the motor was,
4) replace the pot on the servo with with a rough middle-range equivalent (i.e. if it's a 1k ohm pot, replace it with a 500 ohm one. Yes, there is soldering involved. )
5) plug in your shiny new motor to the other end of the h-bridge and turn on your Tx/Rx
6) adjust your trim until the motor stops moving


If you have any experience with electronics, this shouldn't be difficult. In fact, I built a 50-amp brushed esc (using ebay components) for less than $12. Perhaps not the most reliable, but it works.
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Old 07-25-2011, 01:43 PM   #13
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Quote:
Originally Posted by aarcobra View Post
Boy this discussion brings back some memories!!! Since I'm so old and have been involved inmost phases of RC Car Racing since about 1970, I can tell you that it is not only possible but was angiant leap forward!

Some quick background: The first 1/12 scale R/C cars were nitro (we called them "gas") with Cox .049 engines and hard plastic bodies...Jerobee Cars. those of us in the the Midwest couldn't race 1/8 gas in the winter and some guys started converting the Jerobee cars to electric. All you needed was a Black & Decker 4.8volt hand-held grass trimmer to go with the Jerobee chassis. My recollection is that Fort Wanye, Indiana, (Wayne Palmer?) Chicago (Roy Moody) and Toledo and Detroit were into this pretty early. There were many early speed controls, I remember Roy's cars using a series of micro-switches and resistors actuated by a "camshaft" connected to a servo. 1/8" Wheel collars on a 1/16" shaft made the cam lobes and switched in 2 resistors, one resistor, and no resistor for 3 speeds! I remember some modified slot car controller resistor/wiper set-ups Rick Davis out of Detroit used and that style became the standard, even had adjustable dynamic brakes!!!
Now to the Servo/ESC. The first one I saw was in Fort Wayne and unfortunately I can't remember the guys name (Rick?) Great guy, neat cars, good driver, and very helpful. He had this very smooth control in his car and it worked really well. (Oh yeah, I think we were still running on slippery floors then with soft foam tires coated with silicone, smooth was good!!) Anyway he gave me the plans and I made some up and some of us in Toledo ran them. I have some of the parts left in my elecronics junk box. It used a Motorola S2000 Power transistor, driven by the servo amplifier removed from the servo. I think there were a few other parts but basically the transistor replaced the motor in the servo and regulated the voltage to the drive motor. We were using Mabuchi can motors, very similar to the closed end bell ones many manufacturers use in the RTR's.

Hey, that reminds me of one ya'll never believe!! We also used a rotary selector switch, kinda like an old click TV tuner, with resistors dropping the voltage to the motor. But before the resistors, we would wire it so first one cell, then two cells, then three cells, THEN all four were switched on for a FOUR Speed Controller!!! Can you even imagine what that did to the balance of the Batteries??? Just about everybody had the cells hard wired into the car and charged for 15minutes between heats. The early chargers were pieces of wire with alligator clips used to limit the current to the pack, then 15 minute timers were added for automatic cut-off. When digital Volt meters came out you could peak charge while watching the rate of voltage increase and then the voltage drop after peak. I swear this is all true!!!

Those were the good old days!!!

Happy Racing,
Ned
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Old 07-26-2011, 09:26 AM   #14
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There is just simply not enough power fets on the servo driver board to handle a larger current load of a any other motor other than the one it was intended for. The lower power fets on them are design specifically for the intended servo and specification and are also priced accordingly. Power fets are expensive!
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Old 08-10-2011, 12:35 AM   #15
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I build them all of the time for 1/87 scale trucks... they actually make a pretty good ESC for that
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